1. Field of the Invention
The invention relates to a random digital generator that relies specially on an arithmetic compressor.
It can be applied for example in industrial devices using pure random numbers. It can be used in games of luck on the Internet, in the RAPIDO system of drawing lots for the French lottery system or again in astronomy computations.
It can also be used in cryptography, since the security of encryption algorithms and of many cryptographic protocols relies on the existence of totally random parameters (such as encryption keys, etc.).
The invention can also be used in secured online procedures (purchasing, teleprocedures, the authentication of documents, etc.) based on the use of an electronic signature that increases requirements in terms of pure “real-time” random numbers. An e-commerce server must indeed be capable of producing several hundreds of electronic signatures per second.
2. Description of the Prior Art
The generation of digital random values by means of an electronic device consists of the more or less direct sampling of an unstable and non-reproducible parameter. This parameter may be the amplitude of an analog signal, the duration between two events, etc.
The random aspect of the information obtained is then related to the characteristics of the original signal and/or the imprecision of the measurement. In present-day practice, industry uses various methods for the generation of random numbers, such as the analog amplification of a noise-ridden signal and the sampling of a clock A with an asynchronous clock B.
The random values generated by these various physical sources generally have characteristic statistical defects, such as defects of equidistribution, the existence of pseudo-periods, etc. The consequence of these defects is that the real entropy of the random value produced is lower than its maximum theoretical entropy (SHANNON's entropy measures the mean information provided by a random variable).
There are several solutions of varying complexity and varying cost that can be used to eliminate these characteristic biases. These solutions include, for example:                The addition of a cryptographic smoothing device downstream to produce a perfect-sequence of random values from a sequence with a higher bit rate having entopic defects. The smoothing device used is, in practice, a pseudo-random generator (PRG) that can be implemented in either hardware or software form depending on the security and bit rate constraints desired. FIG. 1 is a drawing of such a device,        The use of several physical sources in parallel to smoothen the defects.        
Furthermore, the complexity of the different architectures (the implementation of the random generator in two FPGAs) furnishes methods of random generation that are not suited, in terms of throughput, to “real-time” needs for perfect random values.
The patent application EP 1 223 506 describes a random number generator that implements a dictionary-based method of compression. This method is well suited to the compression of high-redundancy sources but not to the compression of binary sequences derived from the sampling of a physical source.
The idea on which the method and device according to the invention are based uses especially the concept of the random extractor. A random extractor is a deterministic device designed to be inserted after a physical random source in order to eliminate its defects.